1. Field of the Invention
The present invention relates to a process of producing stained crystallized glass and its articles. In particular, the present invention refers to a method for obtaining crystallized glass with patterns and colors resembling that of granites, marbles, and other stones, and applying such to an incombustible construction material.
The "crystallized glass" of this invention refers to crystallized glass formed by the softening and deformation of the glass through heat-treatment at a temperature higher than the softening point, simultaneously with needle-like crystals precipitating from the surface of the glass toward the interior part, in a direction normal to the surface. "Crystallized glass" refers to the crystallizable glass having crystals in the interior after heat-treatment, there being a coexistence of glass and crystals as shown in FIG. 5, in which A indicates a crystalline phase of needle-like crystals of .beta.-wollastonite, and B indicates a remaining portion of the crystallizable glass.
2. Prior Art
Crystallized glass obtained by heat-treating crystallizable glass is characterized as having excellent mechanical strength, heat-resistance, chemical corrosion strength, and water resistance, thus it can be used in various fields.
Nowadays, crystallized glass has been used in construction, replacing natural stones due to its excellent characteristics, and has obtained great popularity.
In the prior art, the method of staining crystallized glass is by adding oxide of Fe, Co, Ni, Cu, or Mn . . . etc. to the glass material as a stain. With the application of high heat, the stain is fusion bonded with the glass material. Thus, stained crystallized glass is deformed by the heat-treatment of such crystallizable glass. However, the process of producing crystallized glass has disadvantages as listed below:
1. The stain added in the glass material is consistently an oxide composed of transition elements, such as Fe, Mn, Co, Cu, . . . etc. Most transition elements contain more than two ionic conditions, which usually changes its ionic valence with increasing heat during the crystallization process. The color of crystallized glass will be altered with the alteration of relative capacity between two different ionic charges and results in color aberration. As in the disclosure of Japanese Patent Publication No. 53-39884, black crystallized glass can be obtained by adding Fe.sub.2 O.sub.3 as a stain. However, the following are problems and disadvantages of the process disclosed in Japanese Patent Publication No. 63-201037:
a) During the heat-treatment of the crystallization process, the hue of the stain will be altered with the transfer from Fe.sup.2+ to Fe.sup.3+. Thus, the black hue of crystallized glass comes out unsteady and uneven. PA1 b) For production of an arcuate plate of crystallized glass, a heat-treatment is applied to a previously completed flat crystallized glass plate. A temperature of 800.degree. C..about.900.degree. C. is used to bend the plate, which temperature will absolutely cause the transfer from Fe.sup.2+ to Fe.sup.3+ and result in an obvious color aberration. The color aberration will be more obvious when a flat crystallized glass plate and an arcuate crystallized glass plate are bonded together in an application.
Further, it has been found that while CuO is added to crystallizable glass, as stain for green crystallized glass, the color of the completed crystallized glass is between green and brown in an uneven state, due to the unpredictable alteration of relative capacity of Cu.sup.+ and Cu.sup.2+ in the fusion glass.
2. During the melting process in a furnace, the method of adding an oxide stain to the glass material for producing crystallized glass that only suits production of few varieties in large quantities, instead of production of many varieties in small quantities.
Accordingly, the Japanese Patent Publication No. 5-43651 and Patent Publication No. 130902 of the Republic of China disclose an improvement by mixing crystallizable glass with inorganic pigment prior to the heat-treatment process to produce crystallized glass articles. This prior art indeed reaches the goal of production of many varieties in small quantities, and avoids color aberration owing to the use of an inorganic oxide pigment with property of high heat-resistance, preventing ionization when being heat-treated with the crystallized glass. The step of adding water is used in this process for compounding glass granules and a powdery inorganic pigment, as a batch, that is poured into a refractory mold and formed as stained crystallized glass by a crystallization heat-treatment. In the above described process, water is regarded as a media for compounding glass granules and an inorganic pigment as a batch, which is heat-treated at 1100.degree. C. for an hour to precipitate .beta.-wollastonite in the glass, and fusion bonding the batch into a body. In this process, the softening point of crystallizable glass is at about 700.degree. C. However, the fusion of glass granules begins at 850.degree. C. and the vaporization temperature of water is 100.degree. C. That is to say, the bonding media (water) no longer exists during the heat-treatment of the glass and inorganic pigment at a temperature higher than 110.degree. C. Therefore, when the glass granules get softened, part of the inorganic pigment directly contacts the glass granules and will simultaneously move with the glass granules. While the portion of the inorganic pigment that fails to contact the glass granules will float on the surface of softened glass, because of an absence of an attractive force, and will be isolated like an island in the sea, resulting in a discontinuity of the pigment that causes spots in the completed crystallized glass.